(1) Field of the Invention
The present invention relates to a hinge mechanism and a foldable portable telephone having the hinge mechanism.
(2) Description of the Related Art
A foldable portable telephone 10 is shown in FIGS. 1A, 1B and 1C. The portable telephone 10 generally has a telephone body 11 and a foldable lid 12. The lid 12 is rotatably supported to the body 11 by a hinge 13. The lid 12 is opened away from or closed to the body 11 in rotating directions indicated by arrows "A1" and "A2" in FIGS. 1B and 1C.
A folded condition of the portable telephone 10 when it is not in use is shown in FIG. 1A. When the portable telephone 10 is in the folded condition, the lid 12 is placed in a closed position "P1". The telephone body 11 includes a ten-key portion 14, and the ten-key portion 14 is fully covered with the lid 12 in the closed position P1. The hinge 13 at this time is locked to fix the lid 12 to the body 11.
An unfolded condition of the portable telephone 10 when it is in use is shown in FIG. 1B. The hinge 13 is unlocked before the use of the portable telephone, and the lid 12 is rotated 145.degree. in the direction A1 to an opened position "P2".
There is shown in FIG. 1C a condition of the portable telephone 10 when an external force is accidentally exerted onto the lid 12 in the direction A1, for example, when the portable telephone 10 is dropped. The lid 12 at such a time may be forced to a position "P2" that is 180.degree. away from the body 11. Then, the lid 12 is rotated in the direction A2 from the position "P3" to the position "P2".
It is necessary that the hinge 13 of the foldable portable telephone 10 meets the following requirements:
a) The hinge automatically rotates the lid 12 in the direction "A1" from the closed position "P1" when the hinge is unlocked. PA0 b) The hinge holds the lid 12 at the opened position "P2". PA0 c) The hinge permits the lid 12 to be rotated in the direction "A1" from the position "P2" to the position "P3". PA0 d) The hinge returns the lid 12 back to the position P2 if the lid 12 is rotated in the direction "A1" from the position "P2" to the position "P3". PA0 e) The hinge is small in size. PA0 f) The hinge is built in a module. PA0 g) The hinge includes a damper.
In addition, it is desirable that the hinge 13 of the foldable portable telephone 10 meets the following requirements.
FIG. 2 shows a conventional hinge mechanism 20. The hinge mechanism 20 includes a pipe 21, a first helical torsion spring 22, a second helical torsion spring 23, and a connecting unit 24. The hinge mechanism 20 is used as the hinge 13 of the foldable portable telephone 10 in FIGS. 1A through 1C. In FIG. 2, the elements which are the same as corresponding elements in FIGS. 1A through 1C are designated by the same reference numerals.
The hinge mechanism 20 rotates the lid 12 in the direction "A1" to the opened position "P2" by using a resilient biasing force of the first helical torsion spring 22.
The hinge mechanism 20 returns the lid 12 back to the position "P2" by using a resilient biasing force of the second helical torsion spring 23 if the lid 12 is excessively rotated in the direction "A1" toward the position "P3"
The first helical torsion spring 22 has an arm portion 22a at one end of the spring 22, and the arm portion 22a is fitted in a slit 25a of a shaft 25. The shaft 25 is secured to the telephone body 11. The first helical torsion spring 22 has an arm portion 22b at the other end of the spring 22, and the arm portion 22b is brought into contact with the top of a plate 27. The plate 27 is secured to the lid 12.
The second helical torsion spring 23 has an arm portion 23a at one end of the spring 23, and the arm portion 23a is inserted between the lid 12 and the bottom of the plate 27. The second helical torsion spring 23 has an arm portion 23b at the other end of the spring 23, and the arm portion 23b is inserted to a hole 24a of the connecting unit 24.
The connecting unit 24 is rotatably supported on the shaft 25. The connecting unit 24 has a projection 24b, and a rotation of the connecting unit 24 on the shaft 25 is restricted by a connection of the projection 24b to a stopper 28. The stopper 28 is secured to the telephone body 11.
When the hinge mechanism 20 is locked to fix the lid 12 to the body 11 at the closed position "P1", as shown in FIG. 1A, the arm portion 22b is fixed and the first helical torsion spring 22 is twisted. A rotation of the connecting unit 24 on the shaft 25 is possible, and the arm portion 23b of the second helical torsion spring 23 is not fixed. The second helical torsion spring 23 is not twisted.
When the hinge mechanism 20 is unlocked, the lid 12 is rotated from the position "P1" in the direction "A1" due to the biasing force of the spring 22. The connecting unit 24 at this time is freely rotated on the shaft 25.
When the connecting unit 24 is rotated on the shaft 25 until the projection 24b touches the stopper 28, the biasing force of the spring 23 starts to act on the connecting unit 24 against the biasing force of the spring 22. The rotation of the lid 12 to the body 11 is stopped when the biasing force of the spring 23 and the biasing force of the spring 22 are in an equilibrium condition. The lid 12 is held at the opened position "P2".
FIG. 3 shows a condition of the hinge mechanism 20 in which the lid 12 is held at the position "P2". In FIG. 3, the biasing force "F1" of the spring 22 and the biasing force "F2" of the spring 23 are in an equilibrium condition.
When an external force is accidentally exerted onto the lid 12 in the direction "A1" at the position "P2", the lid 12 is further rotated in the direction "A1" to the position "P3" by the external force against the biasing force of the spring 23.
When the external force is no longer exerted on the lid 12, the lid 12 is rotated in the direction "A2" toward the position "P2" due to the biasing force of the spring 23.
FIGS. 4A and 4B show a conventional locking member 30. The locking member 30 includes a push button 31, a locking unit 32, a helical tension spring 33, and a helical compression spring 34. The locking member 30 is used to lock or unlock the hinge mechanism 10.
In FIG. 4A, a condition of the locking member 30 before the push-button 31 is pushed to the right (or in a direction indicated by an arrow X1 in FIG. 4B) is shown. The tension spring 33 is in a compressed state and the compression spring 34 is in an expanded state. The locking unit 32 is depressed by the compression spring 34 in a direction indicated by an arrow U2 in FIG. 4B. A downward extension 32a of the locking unit 32 projects downward from an opening 35.
In FIG. 4B, a condition of the locking member 30 after the push button 31 is pushed by the user to the right to lock the hinge mechanism 20 is shown. The locking unit 32 is pushed by the push button 31 in the direction indicated by the arrow X1 in FIG. 4B. A slot 32b of the locking unit 32 is guided by a pin 36 so that the locking unit 32 is moved up, against a biasing force of the spring 34, in a direction indicated by an arrow U1 in FIG. 4B. The downward extension 32a of the locking unit 32 is retracted upward from the opening 35, and the locking of the hinge mechanism 20 is thereby canceled. If the push button 31 is released by the user, the push button 31 and the locking unit 32 are returned, due to the biasing forces of the spring 33 and the spring 34, respectively, back to their initial positions shown in FIG. 4A.
Accordingly, the above-described hinge mechanism 20 has the following problems.
a) The flexibility of design is restricted.
When the portable telephone 10 is in use, the lid 12 must be held at the position P2 where the biasing force F1 of the spring 22 and the biasing force F2 of the spring 23 are in the equilibrium condition. Suppose that the spring 22 has a spring constant K1 and the spring 23 has a spring constant K2. To allow the lid 12 to be held at the position P2, it is necessary that the springs 22 and 23 meet the requirement: K1&lt;K2. If K1.gtoreq.K2, a position at which the lid 12 is actually held when the portable telephone 10 is in use incorrectly deviates from the position P2.
Therefore, since it is difficult to independently determine the spring constant K1 of the spring 22 and the spring constant K2 of the spring 23, the flexibility of design is restricted.
b) The lid 12 cannot be smoothly moved when it is folded or unfolded.
As described above, the springs 22 and 23 must meet the requirement: K1&lt;K2. It is likely that the lid 12 is rotated from the position P1 to the position P2 too slowly or too quickly. Also, it is likely that the lid 12 moves irregularly.
c) Assembling operations to incorporate the hinge mechanism 20 into the foldable portable telephone 10 is not easily performed.
The hinge mechanism 20 is not built into a module. The assembling operation to incorporate the hinge mechanism 20 in the portable telephone 10 requires a large amount of assembling labor or time.
In addition, the hinge mechanism 20 requires a relatively large size if a connector is included in the hinge mechanism 20.
The above-described locking member 30 is, as shown in FIGS. 4A and 4B, comprised of the push-button 31, the locking unit 32, the helical tension spring 33, and the helical compression spring 34, which are separate independent parts. The locking member 30 requires a relatively large space of the portable telephone. It is difficult to reduce the size of the portable telephone 10 with the locking member 30.